Direct communication between mobile radio communication devices

ABSTRACT

The present invention provides for a wireless communications method and related system and wireless terminal devices arranged for communication between first ( 304, 404 ) and second ( 306, 408 ) wireless terminal devices by way of direct communication, for example by way of a D2D link in a network environment, the method and system and, as appropriate, devices, being arranged to provide for the delivery of link-quality parameter information from at least one of the two terminal devices to the network for communications interaction by the network with communication between for the two terminals in direct communication.

TECHNICAL FIELD

The present invention relates to a direct communication link between twowireless terminals, such as mobile radio communication devices, and inparticular to such devices performing Device to Device (D2D)communication.

BACKGROUND ART

It is currently provided that two wireless terminals, examples of whichaccording to several modern communications standards are referred to asa number of User Equipment (UE) can communicate with one anotherdirectly by means of D2D communication, and which of course is providedin addition to normal network connectivity. It has been suggested thatvaluable services could be provided by Third Generation PartnershipProject (3GPP) wireless communication systems based on UEs being inproximity to each other. Such services could include Public Safetyservices and non-Public-Safety services that potentially would be ofinterest to operators and users.

For example, 3GPP technical report RP-122009, by Huawei and HiSilicon isentitled “Evaluation requirements for D2D”, 3GPP publication FS_ProSe,TR 22.803, and SP-120456-MoU between TETRA & Critical CommunicationsAssociation (TCCA) & the National Public Safety TelecommunicationsCouncil), and S1-121247 (TCCA).

Also, 3GPP publication R1-130133 (ZTE—“Evaluation methodology for D2Ddiscovery”) proposes that D2D-based proximity services (D2D ProSe) couldbe realized within or without 3GPP Long-term Evolution (LTE) networkcoverage, and in both cases detection signals would be used by UEs forD2D proximity direct discovery without position information.

There is currently a need for improvements relating to three technicalaspects of D2D communications: discovery; D2D communication andsignalling (including PHY and MAC layers, control layer and protocoldesign); and mitigation of the effects of noise and interference.Discussions below are concerned mainly with the last two of thesetechnical aspects.

The physical environment in which wireless communication terminals arelocated changes over time. This can be due to changes in position,interference from other base stations or other terminals, power ofreceived signals, distance between terminals, multipath attenuation etc.Also, D2D communication may affect cellular communication byinterference of a signal used in the direct (D2D) communication linkwith signal(s) used in the cellular communication; and/or a D2Dcommunication link may affect other D2D communication links byinterference of a signal used in the direct (D2D) communication linkwith signal(s) used in such other D2D communication links.

Currently, the direct link (D2D link) between two terminals isestablished and maintained by means of signals transmitted between thetwo terminals and control of the quality of the direct link between theterminals is disadvantageously limited.

The present invention seeks to provide for wireless communicationsmethods and related communications systems and terminal devices havingadvantages over known such methods, systems and terminals.

CITATION LIST Non Patent Literature

-   NPL 1: “Evaluation requirements for D2D” 3GPP technical report    RP-122009, by Huawei and HiSilicon.-   NPL 2: 3GPP publication FS_ProSe.-   NPL 3: 3GPP publication TR 22.803.-   NPL 4: 3GPP publication SP-120456.-   NPL 5: 3GPP publication S1-121247 (TCCA).-   NPL 6: 3GPP publication R1-130133 ZTE—“Evaluation methodology for    D2D discovery”-   NPL 7: 3GPP publication TR 36.932.

SUMMARY OF INVENTION Technical Problem

Currently, the direct link (D2D link) between two terminals isestablished and maintained by means of signals transmitted between thetwo terminals and control of the quality of the direct link between theterminals is disadvantageously limited.

Solution to Problem

According to one aspect of the invention there is provided a wirelesscommunications method for communication between first and secondwireless terminal devices arranged to communicate by directcommunication by way of a direct link in a network environment, themethod including the step of delivering direct-link-quality parameterinformation from at least one of the two terminal devices to the networkfor interaction by the network with communication between the twoterminals in direct communication.

The invention can advantageously employ the sending of device to devicemeasurements/statistics associated with one link and one wirelessterminal device in an efficient manner to the network for handling.

The said interaction by the network be employed as required but inparticular can comprise network control of communication between thefirst and second terminal devices, or for example can comprise networkplanning procedures such as for the purpose of Minimization of DriveTests.

The said terminal device can comprise any appropriate device such as awireless network UE, or for example a Low Power Node.

Further, the link-quality parameter information can comprise terminaldevice transmission information and/or terminal device receptioninformation.

Also, the said link-quality parameter information comprises Quality ofService statistics.

According to another aspect of the present invention there is provided amethod of operation within a wireless communications terminal devicearranged for direct communication with a further wireless communicationsterminal device by way of a link in a network environment, the methodincluding the step of delivering link-quality parameter information fromthe said wireless communications terminal device to the network forinteraction by the network with communication between the terminals inthe said direct communication.

As will be appreciated, the said wireless communications terminal devicecan be arranged to deliver a signal in accordance with the generalwireless communications method outlined above.

Further, all aspects of the present invention can involve communicationprovided by way of a 3GPP air interface, or alternatively provided bynon-3GPP technology such as, or example, but not limited to, a Wi-Fi,FlashLinkQ, WiMax or Bluetooth link.

According to yet a further aspect of the present invention, there isprovided a wireless communications system comprising first and secondwireless terminal devices arranged for direct communication by way of alink in a network environment, the system being arranged for delivery oflink-quality parameter information from at least one of the two terminaldevices to the network for interaction by the network with thecommunication between the said first and second wireless terminaldevices in direct communication.

The system can be arranged to operate in accordance with any one or moreof the features of the methods defined and described herein.

That is, in particular, in the system the said at least one wirelessterminal device can be arranged to deliver a signal to the networkcomprising an indication of quality of wireless link between the firstand second terminals, and the said at least one wireless terminal isfurther arranged to receive a wireless command signal for control of thelink-quality perimeter in response to the command signal.

Advantageously, the network control can provided by way of a closedcontrol loop, which, if required, can comprise a slow outer loop. Thecontrol loop can also allow for the collection of current Tx/Txparameters and, if required, give a maximum, range or some other targetlimit.

According to still a further aspect of the present invention there isprovided a wireless communications terminal device arranged for directcommunication with a further wireless communications terminal device byway of a link in a network environment, the said wireless communicationsterminal device being arranged to deliver link-quality parameterinformation to the network for interaction by the network with the saiddirect communication.

Again, the operability of such a device can be consistent with one ormore of the features of the system and methods outlined above.

In particular the present invention finds particular use within a D2Dcommunications environment.

The invention advantageously identifies that D2D power control and/orresource allocation and/or other transmission and reception parameters(such as coding scheme, number of retransmissions, etc.) can beperformed by a cellular wireless network, and doing so can reduceinterference to other user and/or a number of network equipment bycontrolling signals transmitted in a D2D link.

As will therefore be appreciated, the invention proposes that control ofthe quality of a direct communication link between two wirelessterminals be achieved by way of part of a communication networkconnected to at least one of the two wireless terminals. Accordingly, ina general sense, apparatus, systems and methods disclosed herein arearranged to allow for network control of the quality of the direct link.

Also, it should be appreciated that link-quality parameters can be Tx(e.g. power) and Rx (e.g. BLER). In particular Quality is not to beconsidered only QoS, because Tx power is not a QoS parameter. For thecontrol “slow” loop, not only current values (power, BLER,retransmissions) but also control values (generally speaking a target, amax, a range etc) should advantageously be sent.

Further, the commands or the measurement reports can be triggered, orevent based, or periodical.

The above and further features and aspects of the invention and areexplained in more detail, by way of illustration only, in the followingdetailed description of embodiments of the invention and with referenceto the accompanying drawings.

Advantageous Effects of Invention

The present invention can provide for wireless communications methodsand related communications systems and terminal devices havingadvantages over known such methods, systems and terminals.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified representation of a network arrangement of a basestation and plural wireless communication terminals;

FIG. 2 is a simplified representation of a network arrangement of pluralwireless communication terminals which can each transmit a beacon signalfor indicating their presence;

FIG. 3 is a simplified schematic representation of a base station incommunication with a wireless terminal, and another wireless terminalwhich is out of coverage of the base station;

FIG. 4 is a simplified schematic representation of a base station incommunication with a wireless terminal, and another wireless terminalwhich is out of coverage of the base station but within coverage ofanother base station;

FIG. 5 is a simple diagram showing different possible combinations ofinputs and outputs of an algorithm for controlling a link qualityparameter of a D2D link via a base station of a network;

FIG. 6 is a respective flow diagram illustrating the algorithm at a highlevel according to respective possible implementation scheme;

FIG. 7 is a respective flow diagram illustrating the algorithm at a highlevel according to respective possible implementation scheme;

FIG. 8 is a respective flow diagram illustrating the algorithm at a highlevel according to respective possible implementation scheme;

FIG. 9 is an example of a Message Sequence Chart (MSC) for control of aquality link parameter of an Intra-Cell D2D link.

FIG. 10 is an envisaged Message Sequence Chart (MSC) for control of aquality link parameter of an Inter-Cell D2D link;

FIG. 11 is an envisaged Message Sequence Chart (MSC) for control of aquality link parameter of an Out-of-Coverage D2D link, where one of thewireless terminals is out of coverage of a base station;

FIG. 12 is a graph showing how number of retransmissions can affect BLER& SINR;

FIG. 13 is a time/frequency grid representing an example of MCS & RE(Resource Element) resource allocation performed by an eNB under goodsignal path conditions;

FIG. 14 is a time/frequency grid representing an example of MCS & RE(Resource Element) resource allocation performed by an eNB under poorsignal path conditions;

FIG. 15 is a flow diagram representing a further arrangement for thealgorithm;

FIG. 16 illustrates an embodiment that includes the use of a so-calledLow Power Node;

FIG. 17 illustrates an alternative embodiment to that of FIG. 16;

FIG. 18 is a schematic representation of a UE embodying the invention;

FIG. 19 is a schematic representation of a UE according to a furtheraspect of the invention;

FIG. 20 is a schematic representation of a network node according to afurther embodiment of the invention.

DESCRIPTION OF EMBODIMENTS

Turning first to FIG. 1, there is provided a simplified representationof part of a cellular mobile radio communications network including abase station 102 of a cell and arranged to communicate with at least oneof plural wireless communication terminals 104, 106 of the type commonlyreferred to as User Equipment (UE) and which can each transmit a beaconsignal 108 for indicating their presence and can also receive and detectsuch a beacon signal 108 and thereby discover nearby wireless terminals.In this example, UEs 104 are in communication with the base station 102,but UEs 106 may not be in communication with the base station. Inparticular in this illustrated example, the UE 104 shown left of basestation 102 is a legacy device, whereas the UE 104 to the right of thebase station 102 is capable of measuring/receiving a beacon from one ofthe other UEs 106 as noted. Both of the aforementioned UEs 104 and 106comprise enhanced UEs having potential use for UE-R transmission and D2Dpurposes.

FIG. 2 is a simplified representation of plural wireless communicationterminals 106 spaced from one another but proximal to each other, whichcan each transmit a beacon signal 108 for indicating their presence andcan receive and detect such a beacon 108 and thereby discover nearbywireless terminals 106. In this example, the terminals perform discoverywithout interacting with a base station and independent of receiving anysignal from a base station.

Possible scenarios are now explained with reference to FIG. 3 and FIG.4, in which an aspect of the present invention can be employed. Inparticular, detail regarding the use of the link qualitymeasurements/statistics is provided further below.

FIG. 3 is a simplified schematic representation of a cellular networkarrangement employing a base station 302 and which is in communicationwith UE 304. Another UE 306 is illustrated and which is out of coverageof the base station 302, that is UE 306 cannot establish or maintain acommunication link with the base station 302 because the physicalenvironment of the link is adverse, for example the distance to the basestation, and thus the path attenuation between the base station and UE306 is so large that UE 306 cannot receive and decode a signaltransmitted by the base station 302, or vice versa.

In this scenario, where one 306 of the UEs is out-of-coverage, UE 304can nevertheless perform Device-to-Device (D2D) communication with theout-of-service UE 306 under network control, because the network controlcan take place through, or via, UE 304 by means of signalling betweenthe wireless terminal 304 and the base station 302.

FIG. 4 is another simplified schematic representation of a cellularnetwork arrangement (inter-cell D2D scenario) including a base station402 in communication with a UE 404. Another UE 408 is illustrated whichis out of coverage of the base station 402. However, UE 408 is withincoverage of another base station 403. The two base stations 402, 403 arein communication with each other via a network connection as indicatedby double-ended arrow 410, and in this manner the two base stations 402,403 can therefore provide a connection between the two UEs 404, 408 byway of the network connection 410. In the figure, the network connection410 is via an ‘X2 interface’ directly between the base stations.However, the connection could equally be via another network entitycommon to the base stations 402, 403. For example, the base stations mayboth be connected to a common mobility management entity (MME) and insuch a scenario D2D control would be performed by the MME.

In this inter-cell D2D scenario, the UE 404 can initiate and control D2Dcommunication with UE 408 under network control. Furthermore, UE 408 caninitiate and control D2D communication with UE 404 under networkcontrol, because the network control can be achieved by way of UE 408and base station 403.

Thus, one of the UEs initiates and controls the D2D link in order tocommunicate with the other UE via the D2D link and to maintain good oracceptable communication under different D2D link conditions, withoutinterfering unduly with other UEs or network equipment with which it notin communication. The UE achieves this whilst not consuming moreresources than required, such resources including power consumption ofthe UE, and resource block(s) (RB) used by the UE.

In another arrangement (comprising an intra-cell D2D scenario, notillustrated), similar to that shown in FIG. 4, each of the two UEs couldbe within coverage of the same base station 402 which can then provide aconnection between the two terminals 404, 408 without routing any signalfrom either of the wireless terminals via the network to another basestation. In this further arrangement, and comprising an “intra-cell”scenario, either UE 404 or UE 408 can initiate and control the D2Dcommunication.

According to this intra-cell scenario, according to one variant both ofthe two UEs are within coverage of, and may be controlled by, the samebase station e.g. eNB. Example signalling for this variant isillustrated in FIG. 9, which is described in further detail below.

According to another variant of the intra-cell scenario, only one of theUEs is controlled by the base station. Operation of this other variantwould be similar to that of the arrangement illustrated in FIG. 3, andexample signalling according to this other variant is illustrated inFIG. 11, which is described in further detail below.

FIG. 5 is a schematic diagram showing different possible combinationsand alternatives, with respect to inputs and outputs of the algorithm(“ALGO”). With reference to FIG. 3 and FIG. 4, the diagram in FIG. 5shows different possible inputs and outputs of the algorithm when thealgorithm is used by the wireless terminal 304, 404 (UE1) to control,via a “slow outer loop”, a direct wireless link between the wirelessterminal 304, 404 and the other wireless terminal 306, 408 (UE2), viathe wireless terminal 304, 404. With reference to FIG. 4, the samediagram of FIG. 5 applies to using the link control algorithm tocontrol, via a “slow outer loop”, the direct wireless link between thewireless terminal 408 and the other wireless terminal 404 (UE1) via theother wireless terminal 408.

D2D link quality measurements and/or statistics may include transmission(Tx) and reception (Rx) D2D statistics of two devices (wirelessterminals) involved in communications via a D2D link, and may be sent tothe network for the purposes of network control of the D2D wireless linkand/or MDT (Minimization of Drive Tests).

During MDT tests, the network obtains performance statistics during aso-called ‘drive test’ during which a UE is used as a testing meanswhile it is deployed in one or more locations in the network coveragearea. The one or more locations typically include multiple locationsalong a drive route along which the UE is transported for example in avehicle.

Control of the D2D link by the network is possible because the networkhas a global view of the status of various devices in the network. Forexample for the inter-cell scenario described above in relation to FIG.4, the base station 402 knows when UE resending information is redundantand affects Quality of Link (QoL) of D2D and the base station 402 cantherefore decide which link is bad and how to control UE1 transmission(Tx) and UE2 reception (Rx). Similarly, for intra-cell scenario the basestation controls both UE1 and UE2 transmissions (Tx) and reception (Rx).This would be also the case for an out-of-coverage scenario.

On the other hand, and if required, the statistics can optionally bereported only for MDT usage (e.g. network planning). In this case thenetwork does not need to send control commands, but it will use suchstatistics for (further) planning purposes.

The “Fast” Inner Loop and “Slow” Outer Loop can be used together forcontrol of one or more D2D quality-of-link parameter. The principle ofsuch a double-loop is as follows: a “slow” loop is used for D2D resourceallocation, and also transmission and reception parameters under networkcontrol and a “fast” loop is used for link adaptation of D2D to radioconditions which could be limited to the allocated resources provided bythe first “slow” loop.

The “slow” loop takes much longer than the “fast” loop and has somelimits imposed upon it by the network via control signalling from thenetwork. The slow loop imposes a limit, or a target, of allocatedresources. For example, the slow loop can set a maximum power level (MAXPWR) and the fast loop can adapt in response to the maximum power levelthat has been set by the slow loop. The slow loop determines or computesa transmit power for a UE to use for transmitting a D2D signal to theother UE.

The slow loop can, in addition to or instead of specifying a maximumtransmit power, specify a range of values, or a target value, or amaximum value, for one or more other parameters associated with the D2Dlink, for example a modulation scheme, a maximum modulation order, amaximum number of retransmissions, etc.

The slow loop is used to obtain, and relay to the network,information/statistics regarding the D2D link, and to send one or moremessages from the network to the UE, the one or more messages includinga range of values, or a target value, or a maximum value, as describedabove in relation to transmit power control, for one or more linkquality-determining parameters such as order of modulation and others.

On the other hand, the fast loop can adapt the wireless link to changesin the physical environment (e.g. path loss) and can for example useless power than the power that the slow loop determines.

In use of the invention, the “Slow” Outer Loop can be used to controlthe quality of link parameter without any use of a “Fast” Inner Loop.Equally the combination of “Fast” Inner Loop and “Slow” Outer Loop maybe used.

Commands that may be sent through or via the “fast” inner loop, andwhich may be considered to be D2D commands, include: modulation (orModulation Coding Scheme MCS); fast power control; and number ofretransmissions to UE1 or UE2.

Commands that may be sent through or via the “slow” outer loop, andwhich may be considered to be network commands, may include: resourceallocation (e.g. Modulation (MCS) & RBs) and transmission and receptionparameters; maximum allowed power information such as MAX UE1/UE2 D2Dpower or range of UE1/UE2 D2D power or TARGET UE1/UE2 D2D power; MAX #of Retransmissions of UE1/UE2, Move D2D Link to network command.

Power Control and resource allocation are performed by the networkbecause (as explained above): D2D communication may affect classiccellular communication (in Uplink or in Downlink) and/or D2Dcommunication between a pair of UEs. D2D communication may thereforealso affect other D2D communication between another pair of UEs.

Evaluation of delay/latency for the “slow” outer-loop and the “fast”inner-loop has resulted in the following values of various parameters:

-   -   A total of 40-50 ms is used for the <<slow>> outer-loop.    -   10 ms detection time of UE1 by UE2    -   10 ms reporting time (through RRC)    -   10 ms decision time (in eNB)        10 ms command time (through RRC) A total of 10 ms is normally        required for the <<fast>> inner-loop.

If however the slow loop is controlled by the MME rather than by theeNB, the time necessary for slow loop control is even longer and theabove timing values could be at least in the order of 20 ms longer.

The “slow” outer-loop can be justified such as Increase/Decrease D2Dresources and therefore can be dealt only through the network control.Only the network can determine whether to increase or decrease resourceallocation because the network is arranged to reduce, or maintain belowa limit, interference from D2D devices (and D2D communications) to otherD2D devices (and D2D communications) and/or other a number of typicaluser equipment UE network equipment such as eNBs.

It follows that the network can perform control of a D2D link by usingthe slow outer loop to control the fast inner loop. The slow outer loopprovides constraints for the fast inner loop, the fast inner loop beingmore adaptive in its response to physical changes of the D2D link.

The “slow” outer-loop therefore provides a means for the network tocontrol the power and resource allocation and transmission and receptionparameters for a D2D communication link. Such resource allocation mayinclude one or more of position of resources in the time-frequency grid(such as those illustrated in FIG. 13 and FIG. 14), modulation, numberof antennas, number of retransmissions, coding scheme, and several otherparameters.

Two UEs involved in D2D communication under network control are arrangedto send quality-of-service (QoS) measurements or statistics to thenetwork. The physical environment changes over time (i.e., position,interference from other cells or other users, power, distance betweenD2D devices etc., as discussed earlier above) and the network can bearranged to control a D2D communication link with respect to thesephysical changes.

The following statistics (or any combination of them) for networkresource allocation (“Slow” Outer-Loop) can be used for the purposes ofcontrolling a D2D communication link.

Transmission (Tx) Statistics of UE1 (or UE2) transmitting to UE2 (orUE1), can be transmitted by UE1 (or UE2) to the network and can includeone or more of the following: Number of retransmissions “# ofretransmissions”; UE1 Tx power (or UE2); current Modulation and CodingScheme (MCS); D2D Link ID (identity of the D2D link); Transmission Mode,TM (if the network doesn't have means to know it); and other informatione.g. Channel State Information CSI such as CQI (such as coding rate,modulation index and resulted channel efficiency that can be supported),number of antennas, multipath conditions, Precoding Matrix Indicator(PMI), Rank Indicator (RI), Precoding Type Indicator (PTI) etc.

Reception (Rx) Statistics obtained by UE2 (or UE1) transmitted by UE1(or UE2), and sent by UE2 (or UE1) to the network, can include one ormore of: number of NACKs/number of received packet symbols; number ofNACKs/number of received RB; number of ACKs/number of received RB; BlockError Rate (BLER), Packet Error Rates (PER) or Bit Error Rates (BER) orFrame Error Rate (FER); and optionally Reference Signal Received Power(RSRP) or Reference Signal Received Quality (RSRQ) levels of receptionfrom UE1 (or UE2).

As should be clear from the following, Transmission (Tx) statisticswithout Reception (Rx) statistics may not be sufficient for controllingthe link quality of a D2D communication link, and similarly Reception(Rx) statistics without Transmission (Tx) statistics may not besufficient for controlling the link quality.

These statistics may be useful for the “Slow” Outer-Loop (UE1 to eNB toUE2 & vice versa), the “Slow” Outer-Loop being used for allocation ofnetwork resource.

Tx statistics and/or Rx statistics may be sent by a wireless terminal toa network base station to which the wireless terminal is connected, whenthe wireless terminal (e.g. UE1) is connected to another wirelessterminal (e.g. UE2) via a direct (in this case D2D) wirelesscommunications link between the wireless terminals. Depending on thestatistics, the base station sends a command signal to the wirelessterminal for the purpose of controlling a quality link parameter of thedirect wireless communications link.

UE1 Tx statistics may be sent when UE1 resends information to UE2because UE2 is in a high interference region or because UE1 Tx power islow or modulation is of high order or because UE1 does not receive ACKbecause UE1 is in a high-interference region.

UE2 Rx statistics may be sent when UE2 does not receive information fromUE1 because UE2 is in high interference region or UE1 power is low ormodulation is of high order.

Based on these statistics the network can determine one or more ofwhether: the link from UE1 to UE2 is bad/good; the link UE2 to UE1 isbad/good; the bi-directional communication between UE1 and UE2 isbad/good; and UE1 and/or UE2 are in a high interference position.

The network can further send a command signal to perform one or more of:increase/decrease the Target (Maximum) # Retransmissions of UE1, UE2 orboth; increase/decrease the power of UE1, UE2 or both; change the D2Dmodulation scheme of UE1, UE2 or both from 64QAM/QPSK for example toQPSK/64QAM (adaptive modulation): 64QAM→QPSK if link is bad andQPSK→64QAM if link is good; route back to the network the D2Dcommunication: UE1 will communicate with UE2 through the network; changethe resource allocated to D2D (e.g. orthogonal resource or other).

As explained briefly above, Tx statistics without Rx statistics may notbe sufficient, and vice versa. It has been found that that thesestatistics may be useful for the “Slow” Outer-Loop (UE1 to eNB to UE2 &viceversa), the “Slow” Outer-Loop dealing with network resourceallocation and transmission and reception parameters control.

FIGS. 6 to 8 are respective flow diagrams illustrating the algorithm ata high level according to three respective possible implementationschemes.

Reasoning for the following proposed algorithms (alternatives) is asfollows:

-   -   The maximum number of retransmissions (“MAX # of        Retransmission”) may be performed first or second (see FIG. 5        and the associated portion of the description below);    -   MCS & RB allocation may be performed first or second (see FIG. 5        and the associated portion of the description below) on the        basis that MCS & RB Allocation have less impact on network        control;    -   Power (PWR) assignment may be the option before the last option,        on the basis that D2D power control should change not too        frequently, in order to reduce interference to other D2D users        or to the network itself;    -   The <<Move to NW>> command may be treated as the last option in        case nothing else works (please also see the alternative in the        alternatives section).

With reference to each of FIG. 6 to FIG. 8, for simplification purposesthe following part of the description refers to a “slow” outer loopalgorithm for a direct link between wireless terminal 404 and the otherwireless terminal 408, via the wireless terminal 404. It should beappreciated that this would also be applicable to control D2D terminal408 to terminal 404 via terminal 408, and would also be applicable forout-of-coverage and intra-cell scenarios.

Also it should be appreciated that FIG. 6 to FIG. 9 are equallyapplicable to both UE1 and UE2 control if UE1 is inverted with respectto UE2.

FIG. 6 is a flow diagram illustrating the algorithm at a high levelimplemented at a network level e.g. a base station, or, an eNB or MME.

At step 601 the algorithm begins.

At step 602 a determination is made, as to whether the block error rate(BLER) of the D2D link, measured in UE2, is greater than a thresholdvalue (Thr).

When the determination in step 602 is negative (NO), in step 603, thealgorithm does not proceed further since there is no further action toperform.

When the determination in step 602 is positive (YES), in step 604 afurther determination is made as to whether the number ofretransmissions is less than or equal to a specified maximum number ofretransmissions.

When the determination in step 604 is negative (NO), the algorithm movesto step 605, described further below.

When the determination in step 604 is positive (YES), in step 606 thenetwork decides to change the UE1 modulation and coding scheme (MCS) andchange the resource block (RB) allocation, and the algorithm then moveson to step 607.

In step 607, a further determination is made as to whether the order ofthe MCS currently set (according to step 606) is below a minimum orabove a maximum specified order, and cannot be decreased or increasedanymore, or the RB allocation that was changed in step 606 cannot beimplemented due possibly to all resources having already been allocatedto other users in direct communication (if the RB allocation that waschanged was increased), or other users in legacy communication, throughthe network or e.g. for eNB communication.

When the determination in step 607 is positive (YES), the algorithm canmoves to step 611, described further below, which is the first step in afirst alternative of the algorithm, or alternatively can end at step611.

When the determination in step 607 is negative (NO), the algorithm movesto step 608, in which the network transmits a control signal intendedfor UE1, the control signal comprising a command indicating that UE1should or is allowed to increase the order of the MCS by a specifieddecrement below, or increment above, the value currently set and/or toallocate more RBs or less RBs or different RBs and/or which RBs.

Thus, the control signal indicates that UE1 should or is allowed tochange the value of a parameter related to the quality of a D2D linkbetween UE1 and UE2, this parameter being the possibly changed MCSorder.

The algorithm then moves back to step 602.

Step 611, mentioned above, itself comprises the initial step in theremainder of the first alternative of the algorithm. In step 612, adetermination is made, as to whether the number of retransmissions isless than or equal to a specified maximum number of retransmissions.

When the determination in step 612 is negative (NO), in step 613 thealgorithm does not proceed further since there is no further action toperform.

When the determination in step 612 is positive (YES), in step 614 afurther determination is made as to whether the block error rate (BLER)of the D2D link between UE1 and UE2, measured in UE2, is greater than athreshold value (Thr).

When the determination in step 614 is negative (NO), the algorithm movesto step 615, in which the algorithm does not proceed further since thereis no further action to perform.

When the determination in step 614 is positive (YES), in step 616 thenetwork decides to increase the maximum number of retransmissions by aspecified increment, and the algorithm then moves on to step 617.

In step 617, a further determination is made as to whether the maximumnumber of retransmissions can be increased any further than the presentnumber. The determination will depend on delay constraints and systemconstraints which are checked by the network for example with respect tothe service type. As a possible alternative, this aspect could beimplemented at the UE side particularly, for example, if the UE changesservice type wherein delay and system constraints could change. Forexample, if D2D changes the service from data to video streaming whereless delay is required, or as another example upon a change from data tovoice.

When the determination in step 617 is positive (YES), the algorithmmoves to step 618, in which the network transmits a control signalintended for UE 1, the control signal comprising a command indicatingthat UE1 should or is allowed to increase, by a specified incrementrelative to the present value, the maximum number of retransmissions viathe D2D link between UE1 and UE2.

The algorithm then moves back to step 612.

When the determination in step 617 is negative (NO), the algorithm endsin step 619. Optionally, at step 619, the process continues at step 701of FIG. 7, or indeed can start at this location.

FIG. 7 is a flow diagram illustrating another variant of the algorithmat a high level implemented at a network level e.g. a base station or aneNB or a MME.

This part of the algorithm commences at step 701.

In step 702 a determination is made, as to whether the currently setmaximum number of retransmissions is less than or equal to a specifiedmaximum number of retransmissions.

When the determination in step 702 is negative (NO), in step 703, thealgorithm does not proceed further since there is no further action toperform.

When the determination in step 702 is positive (YES), in step 704 afurther determination is made as to whether the estimated current blockerror rate (BLER) of the D2D link, measured in UE2, is greater than athreshold value (Thr).

When the determination in step 704 is negative (NO), the algorithm movesto step 705, in which the network decides to reduce UE maximum number ofretransmissions by a specified decrement below the currently set value.The algorithm then moves to step 708 which is described further below.

When the determination in step 704 is positive (YES), in step 706 thenetwork decides to increases UE1's maximum number of retransmissions bya specified increment above the currently set value. The algorithm thenmoves to step 707.

In step 707, a further determination is made as to whether the maximumnumber of retransmissions can be further increased.

When the determination in step 707 is positive (YES), the algorithmmoves to step 708 for transmitting a command.

In step 708, which is reached when the determination in step 707 ispositive (YES), the network transmits a control signal intended for UE1,the control signal comprising a command indicating that UE1 shouldincrease, or be allowed to increase, the maximum number ofretransmissions by a specified increment above the value currently set.

Thus, the control signal, which can be an increase, decrease or imposedvalue, indicates that UE1 should change the value of a parameter relatedto the quality of a D2D link between UE1 and UE2, this parameter beingthe maximum number of retransmissions.

The algorithm then moves back to step 702.

When the determination in step 707 is negative (NO), the algorithm movesto step 711 which is the first step of this alternative of thealgorithm.

In step 712, a determination is made as to whether the block error rate(BLER) of the D2D link between UE1 and UE2, measured in UE2, is greaterthan a threshold value (Thr).

When the determination in step 712 is negative (NO), in step 713 thealgorithm does not proceed further since there is no further action toperform.

When the determination in step 712 is positive (YES), the algorithmmoves onto step 714.

In step 714 a further determination is made as to whether the transmitpower of UE1 currently set is less than an allowed maximum value (MAXPWR).

When the determination in step 714 is positive (YES), the algorithmmoves to step 715, in which the algorithm does not proceed further sincethere is no further action to perform.

When the determination in step 714 is negative (NO) because the power isequal to, or very close to, the maximum value, in step 716 the maximumallowed transmit power is increased by a specified increment, and thealgorithm then moves on to step 717.

In step 717, a further determination is made as to whether the maximumallowed transmit power is limited. When it is limited, it cannot beincreased any further than the present value. The determination willdepend on interference constraints to other D2D or other legacy UE ornetwork equipment. This can readily be checked by the network whichknows all of the environmental characteristics since it is constantlyreceiving measurement from devices/eNBs etc. The network can also imposepower constraints if the UE does not have sufficient energy or wants toconserve UE energy.

When the determination in step 717 is negative (NO), the algorithm movesto step 718 (requiring the sending of a command which can be anincrease, a decrease or an imposed value), in which the networktransmits a control signal intended for UE1, the control signalcomprising a command indicating that UE1 should increase, by a specifiedincrement relative to the present value, the maximum allowed transmitpower of UE1.

The algorithm then moves back to step 712.

When the determination in step 717 is positive (YES), the algorithmends. Optionally at step 719, the process continues at step 801 of FIG.8, which could also comprise the start of this further aspect of thealgorithm.

FIG. 8 is a flow diagram illustrating another variant of the algorithmat a high level implemented at a network level e.g. a base station or aneNB, or MME.

In this variant the algorithm begins at 801 which can be the second stepof the first or second alternative.

In step 802 a determination is made, as to whether the estimated currentblock error rate (BLER) of the D2D link, measured in UE2, is greaterthan a threshold value (Thr).

When the determination in step 802 is negative (NO), in step 803, thealgorithm does not proceed further since there is no further action toperform.

When the determination in step 802 is positive (YES), in step 804 afurther determination is made as to whether the currently set value ofUE1 transmit power is less than a maximum allowed transmit power atwhich UE1 should transmit.

When the determination in step 804 is positive (YES), the algorithmmoves to step 805, in which the network decides to reduce UE 1's maximumallowed transmit power by a specified decrement below the currently setvalue. The algorithm then moves to step 808 which sends a command fromthe network to the UE as described further below.

When the determination in step 804 is negative (NO), in step 806 thenetwork decides to increase UE 1's maximum allowed transmit power by aspecified increment above the currently set value. The algorithm thenmoves to step 807.

In step 807, a further determination is made as to whether the maximumallowed transmit power can be further increased.

When the determination in step 807 is negative (NO), the algorithm movesto step 808.

In step 808, which is reached when the determination in step 807 isnegative (NO) the network transmits a control signal intended for UE1,the control signal comprising a command indicating that UE1 shouldincrease the maximum allowed transmit power by a specified incrementabove the value currently set.

The algorithm then moves back to step 802.

When the determination in step 807 is positive (YES), the algorithmmoves to step 811 which is the next step in this part of the algorithm.

From step 811, the algorithm moves onto step 812, although alternativelycould start at this step.

In step 812, a determination is made as to whether the estimated currentblock error rate (BLER) of the D2D link, measured in UE2, is greaterthan a threshold value (Thr).

When the determination in step 812 is negative (NO), the algorithmterminates in step 813, as there is no further action to perform.

When the determination in step 812 is positive (YES), the algorithmmoves onto step 814.

In step 814, the network decides to transmit a control signal to UE1comprising a command to move the D2D link to the network, or only toUE1. The algorithm then moves onto step 815.

In step 815, the network transmits a control signal for UE1 comprising acommand for UE1 and/or UE2 for the commanded UE(s) to move to thenetwork.

In step 819, the algorithm ends.

Referring back to FIG. 5, it was noted that the UE2 inputs ReferenceSignal Received Power (RSRP) and Reference Signal Received Quality(RSRQ) are optional. With regard to the algorithm of FIGS. 6 to 8however, possible adoption could be as follows. A further loop could beintroduced based on either a comparison with an RSRP target or RSRQtarget, or a comparison with minimum RSRP or RSRQ values noted.Alternatively, the noted condition UE2 BLER>Thr could be replaced withUE2 RSRP or RSRQ<Thr.

FIGS. 9 to 11 illustrate Message Sequence Charts (MSC) for differentscenarios. In FIGS. 9 to 11, information regarding the Modulation CodingScheme (MCS) has been removed for the sake of clarity and conciseness.UE1 and UE2 communicate with one another via a direct wireless link (D2Dlink).

FIG. 9 is an example of a Message Sequence Chart (MSC) for control of aquality link parameter of an Intra-Cell D2D link.

FIG. 10 is an example of a Message Sequence Chart (MSC) for control of aquality link parameter of an Inter-Cell D2D link.

FIG. 11 is an example of a Message Sequence Chart (MSC) for control of aquality link parameter of an Out-of-Coverage D2D link, where one of thewireless terminals is out of coverage of a base station, as shown inFIG. 3 (306).

In each of FIGS. 9 to 11, signalling messages are shown which aretransmitted between a UE (UE1) 902, 1002, 1102 involved in a D2D linkand another UE (UE2) 904, 1004, 1104 also involved in the D2D link.Signalling is also shown that occurs between the respective UEs (UE1,UE2) and a first eNodeB (eNB1) 906, 1006, 1106. Additionally, for theinter-cell scenario shown in FIG. 10, signalling is shown to and from asecond eNodeB (eNB2) 1008.

While the aforementioned drawings relate to a scenario in which UE1configuration occurs in a serial manner before UE2 configuration, inpractice it is also possible and applicable that the configuration ofUE2 could occur in a serial manner before that of UE1, or indeed bothconfigurations could occur in parallel. Equally, the invention alsoprovides that only one configuration might occur per D2D link.

Such options and alternatives are also applicable when the network actsto stop the connection. That is UE2's connection could be stopped beforethat of UE1, or indeed both connections could be stopped in parallel.Equally, the invention also provides that the network sends only asingle message to both UEs (message per D2D link) to stop D2Dcommunication.

FIG. 12 is a graph of BLER or PER versus different requiredsignal-to-interference and noise ratio (SINR) for different numbers ofretransmissions, showing how number of retransmissions can affect BLER &SINR. Each Retransmission improves SINR quality but increasescommunication delay & may require more resources to be allocated.

The uppermost curve 1202 is a graph of BLER or PER versus SINR for afirst retransmission, the next curve 1204 is a graph of BLER or PERversus SINR for a second retransmission, the next curve 1206 is a graphof BLER or PER versus SINR for a third retransmission, and the lowermostcurve 1208 is a graph of BLER or PER versus SINR for a fourthretransmission.

FIG. 13 is a time/frequency grid representing an example of MCS & RE(Resource Element) resource allocation performed by an eNB, andrepresentative of experimentation performed within the context of theinvention under good signal path conditions (providing a low errorrate). In the figure, time is represented on the horizontal axis fromleft to right and frequency is represented on the vertical axis, andeach small rectangle represents a resource element of a resource block.Resource elements 1302, labelled NP, are allocated to network pilotsignals, resource elements 1304, labelled D2D, are allocated to D2Dcommunications signals; and resource elements 1306, labelled OC, areallocated to other communications signals.

Initially only two resource elements were allocated for D2Dcommunication using 64QAM (2{circumflex over ( )}6=>a 64QAM symbol has 6bits of information) in the time/frequency grid.

Note that current 3GPP standards only allows resource allocation byallocating whole resource blocks, each block comprising 12 subcarriers,7 symbols for normal cyclic prefix (CP) configuration, or 6 symbols forExtended CP configuration. The current 3GPP standards do not provide forresource allocation by Resource Element, respective Resource Elementsbeing represented by respective individual rectangles in FIG. 13 andFIG. 14.

FIG. 14 is another time/frequency grid representing an example of MCS &RE (Resource Element) resource allocation performed by an eNB, accordingto further experimentation, but under poor signal path conditions(causing high initial error rate). The eNB had initially allocated ahigher modulation scheme, 64QAM, when the link quality was good. Becauseof the subsequent poor link quality, the eNB then allocated a lowermodulation scheme because a QPSK-modulated signal is much more resistantto noise and interference than a 64QAM-modulated signal.

However, a penalty of using QPSK is that a QPSK symbol has only two bitsof information and is therefore three times more resource-consuming than64QAM (it uses three times as many bits of information). Therefore,three times as many resource elements are used as in the case of goodsignal conditions. This represents a potential problem.

In this poor-signal situation, the resource allocation is performed bythe network insofar as the network should ensure that such decision isnot taken at the UE which could interfere with other UEs or networkequipment. The network must allow such allocation to the UE, in order toensure that the UE does not interfere with other equipment (UE and/ornetwork equipment). This can be because if the modulation scheme werenot changed to a lower order, it would be necessary to increase thetransmit power to a level that would cause such interference with otherequipment. Also, if nearby RBs or Resource Elements (REs) are alreadybusy, the network has to decide which extra RBs or REs to allocate whengoing from 64QAM to QPSK.

In the figure, a group 1405 of six resource elements are allocated tothe D2D link, as compared to the two resource elements 1302 allocated inFIG. 13.

The invention alleviates this problem by ensuring that the link qualityremains good. FIG. 15 is a flow diagram representing an algorithm thatmay be used in addition to one or more of the algorithms describedabove, for example in relation to FIG. 5 to FIG. 8. For example,according to a variation of the algorithm illustrated in FIG. 6, whenthe determination in step 602 is negative, instead of carrying out thestep 603, the algorithm illustrated in FIG. 15 may be executed, and thenthe algorithm illustrated in FIG. 6 would return to the beginning step601. That is, the algorithm starts at 1501 and then proceeds to adetermination at 1502 of whether BER or PER UE2, is higher than THr. Ifso, it proceeds to 1504 for a decrease of retransmissions of UE1, or useof a higher modulation scheme. If at 1502 it is determined that BER orPER UE2 is not less than Thr, then it proceeds to 1503 to increaseretransmissions of UE1 or a change in modulation scheme.

FIG. 16 illustrates an embodiment that includes the use of a so-called“Low Power Node” (LPN) 1602 instead of a user equipment (UE) forcommunicating via a D2D link 1604 with a UE 1606. A Macro eNB 1604communicates, using a Radio Resource Management (RRM) entity 1608, witha Mobility Management Entity (MME) 1610 and also with the Low Power Node1602. In this embodiment, the LPN 1602 can function in the same way asone (304; 404) of the two UEs (304, 306; 404, 408) functions, asdescribed above for example in relation to FIG. 3 and FIG. 4, in orderto transmit D2D link quality data to the network. Equally, the LPN canfunction in the same way as one (304; 404) of the two UEs functions, asdescribed above, to control the link quality. In the embodiment shown inFIG. 16, the Radio Resource Management (RRM) entity 1608 is acentralized RRM.

According to an embodiment, the interface 1612 between a Macro eNB andthe LPN is similar to, but not identical to, a so-called “X2 interface”that is used between base stations. It is envisaged that the LPN 1602may have functionality that is similar to that of a base station entity.The arrows 1612, 1614 in FIG. 16 represent control signalling which iscontrolled by means of the Radio Resource Management (RRM) entity 1608of the network. Also arrow 1616 represents interface between MeNB 1604and UE 1606.

FIG. 17 illustrates another embodiment similar to that shown in FIG. 16.In the embodiment shown in FIG. 17, the Radio Resource Management (RRM)entity 1708 is a distributed RRM with single Radio Resource Controlprotocol.

The Low Power Node (LPN) 1602 may be a device or entity that is largelyin accordance with the 3GPP document TR 36.932, which states:

-   -   “A low-power node generally means a node whose Tx power is lower        than macro node and BS classes, for example Pico and Femto eNB        are both applicable. Small cell enhancements for E-UTRA and        E-UTRAN will focus on additional functionalities for enhanced        performance in hotspot areas for indoor and outdoor using low        power nodes.”

Use of the LPN would allow increase of the coverage of the Macro eNB,which is another possible scenario in RAN2. Also the use of LPN is apossible scenario for use in RAN2 SCE (Small Cells Enhancements).

Another envisaged embodiment comprises at least one UE-Relay (UE-R)which is a UE with relaying capability. The UE-R may relay informationto another UE-Relay or to the eNB. Thus, the UE Relay can act in thesame way at one (304; 404) of the two UEs (304, 306; 404, 408)functions, as described above for example in relation to FIG. 3 and FIG.4, in order to transmit D2D link quality data. Equally, the UE-Relay canfunction in the same way as one (304; 404) of the two UEs functions, asdescribed above, to control the link quality.

This embodiment would be able to function in a similar way to theembodiment described above in relation to FIG. 3 (out-of-coverage case)but the out-of-coverage UE could also perform data communication withthe network through the (one or more) UE-R, for example by means ofeither a single UE-R or a multi-hop transmission through multiple UE-Rs.

The claims, the above detailed description and the accompanying drawingstogether provide a technical teaching that makes it possible to put theinventive subject matter into practice.

The subject matter of the invention provides for a wireless terminalsending D2D measurements associated with one link and one wirelessterminal.

The subject matter of the invention can also provide for a wirelessterminal sending an indication of the type of D2D measurements which itsends.

The subject matter of the invention can also provide for the use of adouble-loop comprising a “slow” loop for resource allocation, andtransmission and reception parameters, and another, “fast” loop for linkadaptation to radio conditions in the limit of the allocated resourceallocation by the slow loop. As an example, the outer loop can set themaximum power to 100 mW and the faster loop adapts to this constraint,e.g. 99 mW if the environment is bad, or to 10 mW if the environment isgood enough. This serves to prevent the UE1 transmitting to another UE2with a power higher than the network allows.

However, with an alternative command, when eNB instead configures atarget, the UE can increase and decrease the value around this imposedtarget (it can be below and above but converging to the target).

The slow loop imposes a limit of allocated resources and transmissionand reception parameters. For example, the slow loop may set maximumpower and the fast loop may adapt responsive to this setting of maximumpower. However the fast loop can adapt to changes in the physicalenvironment and can, for example, use less power than the power computedby the slow loop. The slow loop could also specify a range of values ora target value of power. Equally the slow loop could also specify amaximum value, range of values or target value for one or more otherparameters that affect the quality of the D2D link, e.g. a maximumnumber of retransmissions.

The invention provides for a wireless terminal sending D2D link qualitymeasurements and/or statistics to a network.

The network may use such quality measurements and/or statistics for apurpose such as MDT and/or network planning.

The network may use such quality measurements and/or statistics for apurpose such as “slow” outer-loop control.

Several possible algorithms of control and associated control elementshave been described, along with signalisation schemes for implementingthe invention.

Possible implementation alternatives will now be described briefly.

Respective UEs in communication via a D2D link may use uplink (UL)and/or downlink (DL) 3GPP Long Term Evolution (LTE) resources.Intra-cell, inter-cell or out-of-coverage scenarios are envisaged. Theinformation relating to quality of the D2D link may be computed and sentper Wide-Band or per Sub-Band. For example, the quality of the link canbe determined on all the resource blocks used by D2D, or only in oneresource block used by D2D. Further, information relating to quality oflink per frequency band, whether wide or narrow. Further information canbe sent relative to a physical RB index or a physical RB number, or arange of physical RB indexes.

At least one implementation may include decrease of power or resourceallocation instead of increasing power and resource allocation. It isenvisaged to use only BLER (Block Error Rate) or only informationrelating to maximum number of retransmission(s) and not necessarily acombination of both BLER and maximum number of retransmission(s) (asshown in FIG. 6). As part of power (PWR) assignment, a range of power(e.g. a low limit and/or a high limit) may be specified. A target(variation around this value) may be specified. A maximum power may bespecified. Any combination of Step 0, 1, 2, 3 (preferably in the sameorder), e.g. only 0 & 3 could be provided.

In FIGS. 6 to 8, “<” can be replaced with “<=” (e.g. Steps 1 & 2) and insome cases even with “>”. Equally, “>” could also be replaced with “>=”or “<”.

Another condition could be specified: [“If Time<Thr”=YES], which has alogical value of “TRUE” when “Time” is less than a threshold value“Thr”, and when the value is TRUE a command is not sent. This would havethe advantage of not reporting to often, or not sending configurationcommands too often. It is envisaged that a time may be set to triggerfor reports and for commands.

Offsets and hysteresis values may be added to the conditions.

It is envisaged that, in at least one implementation, a MME or othernetwork entity controls the “slow” outer-loop, and not eNB.

The information relating to link quality may be transmitted in at leastone message via RRC signalling or other similar configuration/reportingmessages such as PUCCH, PUSCH or other, as used in 3GPP.

The configuration & reporting may be done periodically or by triggeredevents (periodically or aperiodically). Instead of PER (Packet ErrorRate), BLER (Block Error rate) or BER (Bit Error rate) or FER (FrameError Rate) or any other similar error rate parameter may be used totransmit the information relating to link quality.

Rx quality measurements RSRQ and RSRP could be used to improve D2Dstatistics.

It is envisaged to use statistics such as CQI (channel qualityindicator), Estimated CQI (ECQI), Channel Condition Number (CN),Physical-Layer Throughput (ETPUT), RF path, PMI (precoding matrixindicator), RI (Rank Indicator) reported by UE for channel condition andBSR (Buffer Status Report) included in MAC frame.

It is also envisaged to use statistics such as Transmission Mode (TM)type e.g. TM1 to TM8 (or other from any further 3GPP releases) if theD2D link uses a TM which can't be identified by the network.

“MOVE to NW” command: Instead of moving the connection to the network,the network could allocate dedicated (more orthogonal) resources byindicating other RBs or other Resource Elements (REs) in the LTEtime/frequency resource grid.

Use of other air interface technologies, other than 3GPP, is envisaged,to transport the signals described above, in particular the signalstransmitting the information relating to the link quality informationand the command signal from the network. Equally, it is envisaged thatnon-3GPP technology, such as Wi-Fi, or FlashLinQ or WiMax or Bluetoothor others may be used to provide the D2D wireless link between two D2Ddevices.

Turning now to FIG. 18, there is provided a schematic view of a D2Doperative UE capable of controlling other UEs and comprising an Antenna1801, Transceiver circuit 1802, User interface 1803, controller 1804,memory block 1805 itself comprising an Operating system, software 1806,a communications control module 1807 for D2D and eNB, which is alsoresponsible of changing the Tx and Rx parameters upon the commandsreceived from the eNB or other UEs, a measurement module 1808 to measureD2D Rx and Tx statistics for eNB upon the configuration message receivedfrom eNB directly from eNB or through another UE (and to be senddirectly to eNB or through other UE), a reporting module 1809 to reportto eNB the D2D Rx and Tx statistics, and a configuration module 1810 toconfigure D2D UEs out of coverage or which are not under network control(upon the configuration message received from eNB directly from eNB orthrough another UE).

With regard to FIG. 19, there is provided a schematic illustration ofUEs of the invention but operative in a manner not capable ofcontrolling other UEs. The UE comprises an Antenna 1901, Transceivercircuit 1902, User interface 1903, controller 1904, and memory block1905 itself comprising operating system software 1906, communicationscontrol module 1907 for D2D and eNB and which is also responsible ofchanging the Tx and Rx parameters upon the commands received from theeNB or other UEs, measurement module 1908 to measure D2D Rx and Txstatistics for eNB upon the configuration message received from eNBdirectly from eNB or through another UE (and to be send directly to eNBor through other UE), and reporting module 1909 to report to eNB the D2DRx and Tx statistics.

Turning lastly to FIG. 20, there is provided a schematic representationof a network node according to an embodiment of the invention such as aneNB and comprising an antenna 2001, a transceiver circuit 2002, networkinterface 2003 (with other eNB or MME etc. for another alternative whenMME controls), controller 2004, and a memory block 2005 itselfcomprising an Operating system software 2006, a communication controlmodule 2007 for communication with UE, D2D, other eNB, NW. (D2Dcommunication block & legacy communication block with UE or eNB, etc), ameasurement configuration module 2008 to send Configuration Messages toD2D (and other UE) and to receive Reconfiguration complete messages, anda control module 2009 to control Tx and Rx parameters for D2D UE.

This application is based upon and claims the benefit of priority fromUnited Kingdom Patent Application No. 1305824.3, filed on Mar. 28, 2013,the disclosure of which is incorporated herein in its entirety byreference.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a direct communication linkbetween two wireless terminals, such as mobile radio communicationdevices, and in particular to such devices performing Device to Device(D2D) communication.

REFERENCE SIGNS LIST

-   102 BASE STATION-   104 WIRELESS COMMUNICATION TERMINAL-   106 WIRELESS COMMUNICATION TERMINAL-   108 TRANSMIT A BEACON SIGNAL-   302 BASE STATION-   304 USER EQUIPMENT-   306 USER EQUIPMENT-   402 BASE STATION-   403 BASE STATION-   404 USER EQUIPMENT-   408 USER EQUIPMENT-   410 NETWORK CONNECTION-   1202 BLER OR PER VERSUS SINR FOR A FIRST RETRANSMISSION-   1204 BLER OR PER VERSUS SINR FOR A SECOND RETRANSMISSION-   1206 BLER OR PER VERSUS SINR FOR A THIRD RETRANSMISSION-   1208 BLER OR PER VERSUS SINR FOR A FOURTH RETRANSMISSION-   1302 RESOURCE ELEMENTS, LABELLED NP-   1304 RESOURCE ELEMENTS, LABELLED D2D-   1306 RESOURCE ELEMENTS, LABELLED OC-   1405 A GROUP OF SIX RESOURCE ELEMENTS ALLOCATED TO THE D2D LINK-   1602 LOW POWER NODE (LPN)-   1604 D2D LINK-   1606 USER EQUIPMENT-   1604 MACRO ENB-   1608 RADIO RESOURCE MANAGEMENT (RRM) ENTITY-   1610 MOBILITY MANAGEMENT ENTITY (MME)-   1612 LPN INTERFACE BETWEEN A MACRO ENB AND THE LPN-   1614 REPRESENT CONTROL SIGNALLING-   1616 REPRESENTS INTERFACE-   1708 DISTRIBUTED RRM WITH SINGLE RADIO RESOURCE CONTROL PROTOCOL-   1801 ANTENNA-   1802 TRANSCEIVER CIRCUIT-   1803 USER INTERFACE-   1804 CONTROLLER-   1805 MEMORY BLOCK-   1806 SOFTWARE-   1807 COMMUNICATIONS CONTROL MODULE-   1808 MEASUREMENT MODULE-   1809 REPORTING MODULE-   1810 CONFIGURATION MODULE-   1901 ANTENNA-   1902 TRANSCEIVER CIRCUIT-   1903 USER INTERFACE-   1904 CONTROLLER-   1905 MEMORY BLOCK-   1906 COMPRISING OPERATING SYSTEM SOFTWARE-   1907 COMMUNICATIONS CONTROL MODULE-   1908 MEASUREMENT MODULE-   1909 REPORTING MODULE-   2001 ANTENNA-   2002 TRANSCEIVER CIRCUIT-   2003 NETWORK INTERFACE-   2004 CONTROLLER-   2005 MEMORY BLOCK-   2006 OPERATING SYSTEM SOFTWARE-   2007 COMMUNICATION CONTROL MODULE-   2008 CONFIGURATION MODULE-   2009 CONTROL MODULE

The invention claimed is:
 1. A method, performed by a user equipment(UE) configured to communicate with a base station and furtherconfigured to communicate with a second UE using a direct link, themethod comprising: determining a value of reference signal receivedpower (RSRP) for the direct link; further reporting, to the basestation, a plurality of parameters related to communication via thedirect link, for initiation of an assignment of dedicated resources fora corresponding direct link communication; receiving, from the basestation, a radio resource control (RRC) configuration message comprisingconfiguration information indicating resources to be used for the directlink communication; and when the second UE is outside of a coverage ofthe base station, and based on a comparison of the determined value ofthe RSRP for the direct link with a threshold, transmitting direct linkcontrol information comprising configuration parameters to the second UEvia the direct link communication.
 2. A user equipment (UE), configuredto communicate with a base station and further configured to communicatewith a second UE directly using a direct link, the UE comprising: atransceiver circuit which receives a reference signal via the directlink; and a processor configured to determine a value of referencesignal received power (RSRP) for the direct link and to control thetransceiver circuit to report, to the base station, a plurality ofparameters related to communication via the direct link, for initiationof an assignment of dedicated resources for a corresponding direct linkcommunication; wherein the transceiver circuit further receives, fromthe base station, a radio resource control (RRC) configuration messagecomprising configuration information indicating resources to be used forthe direct link communication; and wherein, when the second UE isoutside of a coverage of the base station, and based on a comparison ofthe determined value of the RSRP for the direct link with a threshold,the processor is further configured to control the transceiver circuitto transmit direct link control information comprising configurationparameters to the second UE via the direct link communication.
 3. Awireless communications system comprising: a first user equipment (UE);a second UE; and a base station wherein the first UE is configured tocommunicate with a base station and further configured to communicatewith a second UE using a direct link; wherein the first UE comprises: atransceiver circuit which receives a reference signal via the directlink, and a processor configured to determine a value of referencesignal received power (RSRP) for the direct link and to control thetransceiver to report, to the base station, a plurality of parametersrelated to communication via the direct link, for initiation of anassignment of dedicated resources for a corresponding direct linkcommunication; wherein the base station comprises: a transceiver circuitconfigured to receive, from the first UE, the plurality of parametersrelated to the communication via the direct link, a processor configuredto determine configuration information indicating a plurality ofresources to be used for the direct link communication and transmits, tothe first UE, a radio resource control (RRC) configuration messagecomprising the configuration information indicating the plurality ofresources to be used for the direct link communication; wherein, whenthe second UE is outside of a coverage of the base station, and based ona comparison of the determined value of the RSRP for the direct linkwith a threshold, the processor of the first UE is further configured tocontrol the transceiver to transmit direct link control informationcomprising configuration parameters to the second UE via the direct linkcommunication.